It's finally arrived this week - a big brother for my little 80mm Meade ETX-80 refracting telescope, my new Meade 114EQ-AR reflecting telescope! Well, I say 'new' but it's actually a second-hand scope which I bought off eBay for the princely sum of 40 English pounds. Which is not a bad deal, considering these things are retailing around the £200-£300 mark. Just goes to show that astronomy doesn't have to empty your bank account.
Okay - the details! The Meade 114EQ-AR is a long-tube equatorial reflector with a 114mm aperture and 900mm focal length (f/8). It houses an overcoated primary mirror, rack-and-pinion focuser and is borne on a heavy German Equatorial Mount with covered worm gear slow-motion controls, setting circles and latitude control with scale. Don't run away yet - I'll explain some of this technobabble to you later on.
Firstly, the "114" in the name indicates that it has an aperture diameter of 114mm, or four and a half inches, which means it has much more light-gathering power than the three-inch objective lens on my ETX-80. Just compare the diameter of the 114EQ-AR on the right with ETX-80 on the left in the picture below. And more light-gathering power means fainter objects - such as galaxies, nebulae and planetary detail - will appear somewhat brighter.
Secondly, the Meade 114EQ-AR also works differently from the ETX-80. My old ETX-80 is a refractor - the type most people associate with how telescopes work - light goes in through a lens at the top and is focussed into an eyepiece at the other end which you look through. The 114EQ-AR is a classic Newtonian reflector - named after that other Cambridge stargazer. Light enters at the top and hits a spherical mirror at the bottom, where it is reflected to a smaller mirror and eyepiece at the top. Looking at the picture above, you can see that the ETX-80 has an objective lens at the top, while the 114EQ-AR doesn't. You can also see that 114EQ-AR has a mirror at the bottom and its eyepiece is at the top rather than bottom. What difference does all of this make? Well, this means that 114EQ-AR has a longer focal length, which allows for higher magnifications, while the shorter length of the ETX-80 will tend to give wider fields of view. There is one big disadvantage to the set-up of a reflector, however - if you are a five-year old. Because it uses a long tube and the eyepiece is at the top, you won't be able to reach up to the eyepiece to have a look-see - even if you stand on your tippitoes on top of a foot stool!
The other big difference between the ETX-80 and my new 114EQ-AR is the mount. My old ETX-80 has a simple Altitude-Azimuth mount, that is, you move the telescope tube up or down vertically and left or right horizontally to position it to your target. The 114EQ-AR, on the other hand, has what's called a German Equatorial Mount (GEM). You don't move the telescope horizontally and vertically but move it along the polar and equatorial axes of whatever latitude you are situated at. (For more about polar axes, see my bLog entry on Polaris). So you can see in the picture on the right that the telescope itself is tilted to about 52 degrees - the latitude position of my observing site, sunny Longstanton. The setting circles shown in the picture below then allow me to accurately position the telescope to whatever longitude my target is located at.
The big advantage of a GEM for me is in photographing and video capturing my targets. As you read in my blog on Polaris, stars move across your eyepiece's field of view along the polar axis and you have to constantly move your telescope up, down, left and right to keep your target in your field of view. But with your telescope polar aligned, you just need to use the slow motion knob below to keep the object in view along the longitudinal plane - it's already tilted at the right latitude so you don't have to worry about moving it up and down.
So there you have it - the new 114EQ-AR for longer exposures and more light-gathering power for photos of fainter objects such as nebulae, galaxies, star clusters and planetary detail and the old ETX-80 for rich star fields, pin-point stars and splitting binary stars. Two quite different telescopes, with different strengths and weaknesses - but I love 'em both the same!
